1. Field
The present invention relates to a semiconductor integrated circuit including a program circuit of a fuse or the like and a testing method of the same.
2. Description of the Related Art
Generally, after being manufactured, a semiconductor integrated circuit (hereinafter also referred to a chip) is tested and classified as a good chip or a bad chip. A technique of programming a fuse of a bad chip to electrically identify the good chip or the bad chip in a manufacturing process is proposed (for example, Japanese Unexamined Patent Application Publication No. Hei 7-30068, Japanese Unexamined Patent Application Publication No. Hei 11-243124, Japanese Unexamined Patent Application Publication No. Hei 3-225850). Further, a technique of programming a fuse of the good chip to make it possible to electrically identify the good chip or the bad chip in a test mode is proposed (for example, Japanese Unexamined Patent Application Publication No. Hei 10-125742).
Recently, not only the shipment of a packaged chip but also the shipment of chips in a wafer state tends to increase. In this case, a wafer on which good and bad chips are mixed is shipped. In wafer shipment, for example, the surface of the bad chip is marked with ink. Alternatively, a failure map file indicating the position of the bad chip on the wafer is created.
However, if the position of the ink mark is shifted by one chip, the ink mark becomes faint, or a wrong failure map file is created due to a problem in the manufacturing process, a user who has purchased the wafer may be unable to identify the good and bad chips. Further, when a chip which caused the above problem is returned from the user to a semiconductor maker, a long time is sometimes needed to analyze a failure.
Programming the fuse of the bad chip or the good chip is performed to identify the good chip or the bad chip in the manufacturing process of the semiconductor integrated circuit, but does not give consideration to the user who purchases the semiconductor integrated circuit. In order for the user to investigate a program state of the fuse and identify the good chip or the bad chip, the user needs to apply a voltage to a special test terminal (pad) or shift the chip to the test mode.
Further, for example, if only one memory cell is bad in the bad chip, most circuits in the bad chip normally operate. Therefore, it is difficult for the user to identify the good and bad chips in the state where the wrong ink mark is put or the wrong failure map file is created. In particular, in the wafer shipment in which the bad chip is mixed, after a product in which the chip is mounted is assembled by the user, the failure in the chip is sometimes revealed in a test process of the product. After the product is assembled, the ink mark and the failure map file cannot be referred to. Hence, it is difficult for the user to identify whether the chip is shipped as the good chip.